Electrical drying-oven.



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H. J. CARY-CURB.

ELECTRICAL DRYING OVEN.

APPLICATION FILED JULY 25, 191s.

Patented Jan. 6, 1914@ 3 SHEETS-SHEET 2.

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H. J. GARY-CURB.

ELECTRICAL DRYING OVEN.

APPLIATION FILED JULY 25, 1913. 1,083,592. Patented Jan. 6, 1914.

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HENRY a. cnr-cuna, or Enimvnsr, rLLrNors, assranor. To E. n. smeEN'r ,e co., or omesso, ILLINoIs, .s coaroxwrron or ILLINOIS.

`v ELEc'rarcaL nanna-oven.

To all whom it may concern:

Be it known that I, HENRY J. CARY-Conn, a subject of the King of Great Britain, residing atElmhurst, in the county of Dupage and State of Illinois, have invented a new and. useful Improvement'in Electrical Drying-Ovens, of which the following is a speciiication.

- My invention relates to an improvement in electrical ovens of the class used, more particularl in laboratories, for drying chemicals an other'substances.

As its generally described construction, an oven of the kind referred to involves a boxlike ventilated metal-bound shell provided with a hinged door and having its walls formed of suitable heat-insulating material, the box containing shield-forming slabs of heat-resisting material supported over similar slabs, which are wound helically with resistance-Wire to adapt the oven to be heated by including the wires in an electric circuit containing a condenser, usually supported underneath the box, and the purpose of which` is, as usual, to prevent excessive sparking at the switch in breaking the cir cuit. For automatically regulating the temperature in the oven, a thermostat is provided to operate a switch to open the circuit when the heat exceeds a predetermined degree, and permit closure of the same when the heat falls below that degree; and shelves are supported in the box for holding receptacles containing the matter to be dried.

The objectl of my invention is to improve various features in an oven of the construction described, to the primary end of increasin its eiliciency.

the accompanying drawings, Figure 1 shows my im roved drying-oven by a broken view in vert1cal sectional elevation, the section being taken on the line 1 1, Fig. 2; Fig. 2 is a section of the same on line 2, Fig. 1; Fig. 3 is a section on the irregular line 3 3, Fig. 1; Fig. 4 shows one of the wirebound slabs by a plan view; Fig. 5 is an enlarged section on line 5, Fig. 1, and Fig. 6 is a broken enlarged view regarded in the direction of the arrow on line 6, Fig. 1, and

Vshowing a. valve-device in the bottom of the box for regulating ventilation thereof.

Specioation ot Letters Patent.

- application med my su, 191s.- serm no. 701,095.

Patented Jan.c,191'4.

The box 7 shown is of rectangular shape and 1s supported on legs 8. The top, vbottom and side walls of the box, as also its hin ed door 9, are formed preferably'of the insu atmg material-known in the art by the name transita and these parts should be metalbound, as shown, for purposes both of strength and ornamentation. In the top or roofyof the box are provided pipe-equipped o enings 10, 10 for Ventilating 1t, and t rough either of which a thermometer (not shown) may be introduced into the box, when desired, for indicating the temperature therein. Vent-openings, two of which are shown at l1 in Fig. 6, are also provided 1n the box-bottom and are equipped with rotary-disk valves 12 having handles 13 by winch to turn them within limits defined by stops 14 and 15 at the ends of their throw, for uncovering the openings 11, more or less, to regulate ventilation through the box.

A base 16, shown as a rectangular block, and which is made of material highly resistant to heat, preferably a composition of asbestos and cement, is supported at its four corners on the box-bottom, in spaced relation thereto, by screw-legs 17 and nuts 18 embracing the bottom. At intervals along Athe forward and rear edges of the base rise threaded posts 19. Slabs 20 seat at holes in their ends over opposite posts upon metal spacing-sleeves 21 on the latter, the holes being lined with metal thimbles 22 to contact with the upper ends of the sleeves. Similar sleeves 23 about the posts contact at their lower ends with the thimbles, and slabs 24, slightly wider than the slabs 20, having similar holes in their opposite ends, are passed over the pairs of the posts to rest on the upper ends of the sleeves 23; and each pair of the upper and lower slabs is clamped rigidly in place by nuts 25 screwed upon the upper ends of the respective posts. Each slab 20 has an electrical resistancewire 26 wound helically about it, as represented in Fig. 4, with its ends fastened to the opposite thimbles 22 in electrical contact therewith. l

Binding-posts 27 and 28 are provided on the base 16, near one lateral edge thereof, 'for connecting the wiresof the .wound slabs with a source of electric-current, as at a screw-plug 29 having insulating Wires 30 leading from it to the binding-posts.

' Three of the four` posts 19 along the outer edge of the base 16 are electrically connected by a metal strip 31 on the bottom of the base, and similar conducting strips 31 and 32', shown jointedv together, connect the strip 31 with the binding-post'27. The remaining post 19 of this series .of four is not included in the kconnecting strip 31, but is connected with the strips 31, 312, at their junction, by a conducting strip 19. The three corresponding posts 19 along the rear or inner edge of the base 16 are likewise connected by a conducting strip 32, and binding-posts 33, 34, provided on the base near its opposite lateral edge, have insulated-wire connections with a condenser 35 hung rigidly on the bottom of the box for the usual purpose, hereinbefore referred to, of preventing excessive sparking at the switch in breaking the circuit. The remaining, or fourth post 19 of the last-named series of these posts is not included in the strip 32, but' is connected by a conducting strip 192 with a conducting strip 36 shown and connecting the binding posts 33 and 28. Of the last-named series of connected posts 19, that at the right-hand end is connected by a conducting-strip 37 with the binding post 34, which has extending from 1t a conducting strip 38, shown jointed and having a fiat terminal strip 40 curving upwardly and rearwardly from it and jecting backwardly beyond the inner edge of the base. A similar flat terminal-stri 41 is connected by a conducting-strip 42 w1th the binding-post 28. By excluding the two opposite end-posts 1.9 from connection respectively with the strips 31 and 32, but which are electrically connected by the `coil -on their connecting'slab 24, their connections 19 and 192 cause them to be included in the circuit when the switch is opened to cut out the coils on the other slabs 24. As the present oven is desi ed, each unit, comprising a pair of t e strip-connected posts 19, the members of which are connected by a coil-wound slab 24, uses about 1,25 amperes of current, at 110 volts, so that the three units use about 3,1% amperes, which is the maximum that will stand breaking at the switch Withou-t causing excessive sparking. The oven is designed to give a minimum temperature of about 60 C., depending upon the room-temperature. .Whenever, though, the entire number of coils 26 employed is found to be overheating the oven, the coil connecting the two posts 19 that are not electrically connected by the respective strips 31 and 32 is taken out of circuit by removing the slab carrying it, thereby to reduce the temperature. This is the purjointed propose of having the fourth unit out of the control of the switch; though the same result might be accomplished by providing a switch es ecially for cutting out that unit, but the escribed arrangement saves providing the additional switch.

Transversely across the bottom of thev box, underneath the same to be outside of the inuence of the heat within it, extends a rectangular metal bar 43 having a post 44 extending from near its rear end upwardly through the box-bottom, and a ost 45 risin therethrough from near its orward en The post 45, which contains a threaded hole extending through it, near its u per end in the direction transversely of the ox, is split vertically, in that end, to the hole, as shown at 46 in Fig. 2. A cylindrical tubular thermostat-bar 47, having a pointed inner end, holes 48 at intervals or the purpose of aircirculation through it to render uniform the influence thereon of the temperature within the box, and a hand-Wheel -49 on its outer end, is journaled in the front Wall of the box to work at its threaded section 49 in the aforesaid hole in the front ost 45. A shaft 47 journaled in a side o the box to extend at right-angles to the thermostatbar, is threaded at its inner end to work in an alining threaded hole through the split end of the post 45 for releasably locking the bar 47 in any position to which it may be adjusted for the purpose hereinafter explained.

On the upper end of the rear post 44 is rigidly supported, to extend transversely thereof, a metal bar 50. A relatively-heavy metal contact-strip 51 extends at a rightangle to the conducting-strip 42, parallel with and fastened to the face of the bar 50, from which it is shown to be insulated at 52; and it rojects at its free tapered end beyondthe inner edge of its insulating backing. Another relatively-heavy contact-strip 53 is secured at one end to the curved strip 40 to extend in front of and parallel with the face of the bar 50, to which it is fastened at 54. This contact-strip is divided, and its sections are connected by a flat spring 55 of relatively-thin metal. The free, tapered end of the strip 53 overlaps the corresponding end of the contact-member 51 of this switch-device; and the pointed extremity of the thermostat-bar abuts against thei faoe of the contact-member 53, near that en Shelves 56,.preferably of reticulated wire metal-bound about the edges, as indicated in Fig. 1, are supported, to be withdrawably insertible into the oven through its doorway, on ledges 57 provided in the box on its opposite side-walls in tiers above the slabs 24.

I To operate the oven for drying material 51, whereupon the shaft 47 is turned to in receptacles introduced into it on the shelves, and with the door closed and the proper connection made of the plug 29 with a source of electric current, the latter heats the resistance-wires 26 to the required degrec of incandescence for producing the ,desired temperature in the oven. The attainment of this temperature may be ascertained by means of a thermometer inserted through anopening 10. When this temperature has'v been attained, the thermostat-bar, which is then unlocked, is turned to advance its inner end against the contact-member 53 and separate the latter slightly from its companion-member clamp the split end of the post 45 about the thermostat-bar and lock it in its adjusted position. With the oven-door closed, the adjustment of the bar 47 may be performed under inspection of the hot inte-rior of the oven through a mica-covered peep-hole (not shown) in the front wall of the box. With the circuit lthus opened'at the switch, the thermostat-bar shrinks lengthwise sulficiently to permit the contact-member 53, by its vresilient action, to meet the companionmember 51 and again close thecircuit, which remains closed until the resultant heating of the oven becomes slightly excessive and expands the thermostat-bar longitudinally to cause it to open the switch. j

By providing for locking the thermostatbar securely in the adj usted position thereof,

the important advantage is afforded of insuring maintenance of the predetermined heat-condition, and preventing undesirable or'injurious variation therein by accidental or meddlesome turning 'of the bar.v The divided construction of the contact-'member 58 is also of material importance, inasmuch as it enables the connected sections to be made of relatively heavy metal, and the light spring 55 connecting them laffords a resilient joint to Hex and cause the free contacting section of that member to instantaneously and completely break contact with the member 51; whereas, if the member 53 were a continuous piecevof spring-metal, its separation from the companion-member would drag and, by thus failing of instantaneous action, tend to keep the circuit closed until the predetermined temperature became excessive, with injurious consequences to the material under treatment in the oven.

I do not claim herein the thermostatic switch-mechanism for controlling the circuit in the oven, but reserve the right to claim the same in a future application for Letters Patent.

A Another advantage of my improved construction lies in supporting the post-carrying bar 43 outside of the box, where it is not subject to the extending and contracting influence uponvt, were it inside the same, ofthe variations in temperature therein, which would tend to disorganize the parts and render. the action of the thermostat inaccurate and unreliable. Still another'advantage, worth mentioning, is due es A.

below them, since thereby the lowerA slabs 'are shieldingly covered by the relatively wider slabs against spilling on the latter` of the contents of the receptacles, as bv upsetting the same, on shelves 56 while eing introduced into the box or withdrawn, which might tend to impair the resistance-wires or their function.

I realize that considerable variation is possible in the details of construction thus specifically shown and described, and I do not intend by illustrating a single, specific or preferred embodiment` of my improvements to be limited thereto; my intention being in the following claims to claim protection upon all the novelty there may be in my invention as broadly as the state of the art will permit.

What I- claim as new and desire to secure by Letters Patent is 1. An electrical oven of the character described, comprising a box` vented through its top and bottom and having bottom ventopenings provided with a rotary regulating valve, a slab in the box wound with resistance-wire, an electric circuit containing a switch, and automatically-operating means in the box for opening the switch.

2. An electrical oven of the character described,.comprising a box, a slab supported on metal posts in the box and 'wound with resistance-wire, an electric circuit including said wire, 'an electric thermostat-operated switch included in said circuit within the box, and a relatively-wider slab supported on said posts in spaced relation to and covering the wire-wound slab.

3. An electrical oven of the character described, comprising a box, a base supported in the box in spaced relation to its bottom and having opposite metal posts rising from it and surrounded by spacing-sleeves, an electric circuit, a slab having end-openings containing metal thimbles at which it is supported upon the posts on said sleeves, said slab being wound withresistance-wire connected at its ends with said thimbles, and the thimbles being included in said-circuit, an electric switch contained in said circuit, and means for opening and closing the switch.

4. An electrical oven of the character described, comprising a box, a base supported in the box in spaced relation to its bottom and having opposite metal posts rising from it and surrounded by pairs of spacing sleeves, an electric circuit, a slab having endopenings containing metal thim-bles ait which it is supportex upon the posts between said sleeves, saii'd slab being Wound with resistance-Wire connected at its ends with said thimbles and the thimbles being included in said circuit, a slab having end-holes at which it surrounds said posts` and rests onthe upper members of the sleeve-pairs, nuts on the upper ends of the posts for clamping 10 together the parts thereon, an electric switch contained in said circuit7 and means for opening and-closing the switch.

HENRY J. CARY-CURB.

In presence of- NELLIE B. DEARBORN, AMYC. FsoHEn. 

